WO2022244234A1 - Porous-electrode-supporting electrolyte membrane and method for producing porous-electrode-supporting electrolyte membrane - Google Patents

Porous-electrode-supporting electrolyte membrane and method for producing porous-electrode-supporting electrolyte membrane Download PDF

Info

Publication number
WO2022244234A1
WO2022244234A1 PCT/JP2021/019363 JP2021019363W WO2022244234A1 WO 2022244234 A1 WO2022244234 A1 WO 2022244234A1 JP 2021019363 W JP2021019363 W JP 2021019363W WO 2022244234 A1 WO2022244234 A1 WO 2022244234A1
Authority
WO
WIPO (PCT)
Prior art keywords
electrode
electrolyte membrane
porous
reduction
carbon dioxide
Prior art date
Application number
PCT/JP2021/019363
Other languages
French (fr)
Japanese (ja)
Inventor
紗弓 里
裕也 渦巻
晃洋 鴻野
武志 小松
Original Assignee
日本電信電話株式会社
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by 日本電信電話株式会社 filed Critical 日本電信電話株式会社
Priority to PCT/JP2021/019363 priority Critical patent/WO2022244234A1/en
Priority to JP2023522159A priority patent/JPWO2022244234A1/ja
Publication of WO2022244234A1 publication Critical patent/WO2022244234A1/en

Links

Images

Classifications

    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B11/00—Electrodes; Manufacture thereof not otherwise provided for
    • C25B11/02—Electrodes; Manufacture thereof not otherwise provided for characterised by shape or form
    • C25B11/03—Electrodes; Manufacture thereof not otherwise provided for characterised by shape or form perforated or foraminous
    • C25B11/031—Porous electrodes
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B3/00—Electrolytic production of organic compounds
    • C25B3/20—Processes
    • C25B3/25—Reduction
    • C25B3/26—Reduction of carbon dioxide
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B9/00—Cells or assemblies of cells; Constructional parts of cells; Assemblies of constructional parts, e.g. electrode-diaphragm assemblies; Process-related cell features
    • C25B9/17—Cells comprising dimensionally-stable non-movable electrodes; Assemblies of constructional parts thereof
    • C25B9/19—Cells comprising dimensionally-stable non-movable electrodes; Assemblies of constructional parts thereof with diaphragms
    • C25B9/23—Cells comprising dimensionally-stable non-movable electrodes; Assemblies of constructional parts thereof with diaphragms comprising ion-exchange membranes in or on which electrode material is embedded

Definitions

  • the present invention relates to a porous electrode-supported electrolyte membrane and a method for producing a porous electrode-supported electrolyte membrane.
  • Devices related to technologies for reducing carbon dioxide include a reduction device using artificial photosynthesis technology and a reduction device using electrolytic reduction technology.
  • Artificial photosynthesis technology is a technology that advances the oxidation reaction of water and the reduction reaction of carbon dioxide by irradiating an oxidation electrode made of a photocatalyst with light.
  • the electrolytic reduction technique is a technique for advancing the oxidation reaction of water and the reduction reaction of carbon dioxide by applying a voltage between an oxidation electrode and a reduction electrode made of metal.
  • Artificial photosynthesis technology using sunlight and electrolytic reduction technology using electricity derived from renewable energy can recycle carbon dioxide into hydrocarbons such as carbon monoxide, formic acid, and ethylene, and alcohols such as methanol and ethanol. has attracted attention as a technology capable of
  • Non-Patent Document 1 In artificial photosynthesis technology and carbon dioxide electrolytic reduction technology, a reaction system has been used in which a reduction electrode is immersed in an aqueous solution, and carbon dioxide dissolved in the aqueous solution is supplied to the reduction electrode for reduction (Non-Patent Document 1 , 2).
  • this method for reducing carbon dioxide there are limits to the concentration of carbon dioxide dissolved in the aqueous solution and the diffusion coefficient of carbon dioxide in the aqueous solution, which limits the amount of carbon dioxide supplied to the reduction electrode.
  • Non-Patent Document 3 by using a reactor having a structure that can supply gaseous carbon dioxide to the reduction electrode, the amount of carbon dioxide supplied to the reduction electrode increases, and the reduction reaction of carbon dioxide is promoted. be done.
  • the aqueous solution in the reduction tank is removed and the gas - phase carbon dioxide is filled. Therefore, it is necessary to bond the electrolyte membrane and the reduction electrode. Furthermore, since gaseous carbon dioxide cannot reach the interface between the reduction electrode and the electrolyte membrane only by bonding a plate-shaped reduction electrode to the electrolyte membrane, the reduction electrode is made porous so that gaseous carbon dioxide can reach the reduction electrode. It must be possible to reach the interface of the electrolyte membrane. This porous reduction electrode has a problem that if the pore diameter is small, the diffusion resistance of carbon dioxide in the electrode increases, and the efficiency of the reduction reaction of carbon dioxide decreases.
  • the electrolyte membrane When the electrolyte membrane is used as a proton exchange membrane, it is generally immersed in boiling nitric acid and boiling pure water in order to improve the proton mobility of the electrolyte membrane.
  • These treatments are treatments for replacing the proton-exchange groups in the electrolyte membrane with H + , but this treatment causes the electrolyte membrane to be in a swollen state with excessive water content. This is because the electrolyte membrane has a polymer reverse micelle structure, which swells and increases the water content.
  • the present invention has been made in view of the above, and aims to improve the gas phase reduction efficiency of carbon dioxide.
  • a porous electrode-supported electrolyte membrane of one aspect of the present invention is a porous electrode-supported electrolyte membrane used in a gas-phase reduction apparatus for reducing carbon dioxide, wherein the electrolyte membrane is directly bonded to the electrolyte membrane.
  • the porous reduction electrode has an average pore diameter of 1 ⁇ m or more.
  • a method for producing a porous electrode-supported electrolyte membrane according to one aspect of the present invention is a method for producing a porous electrode-supported electrolyte membrane used in a gas-phase reduction apparatus for reducing carbon dioxide, the electrolyte membrane comprising boiling nitric acid and boiling nitric acid.
  • the gas phase reduction efficiency of carbon dioxide can be improved.
  • FIG. 1 is a cross-sectional view showing an example of the configuration of the porous electrode-supported electrolyte membrane of this embodiment.
  • FIG. 2 is a flow chart showing an example of a method for producing a porous electrode-supported electrolyte membrane.
  • FIG. 3 is a view showing an example of thermocompression bonding when manufacturing a porous electrode-supported electrolyte membrane.
  • FIG. 4 is a diagram showing an example of the configuration of a gas-phase reduction apparatus for carbon dioxide provided with a porous electrode-supported electrolyte membrane.
  • FIG. 5 is a diagram showing an example of the configuration of another gas-phase reduction apparatus for carbon dioxide provided with a porous electrode-supported electrolyte membrane.
  • a porous electrode-supported electrolyte membrane 20 of this embodiment will be described with reference to the cross-sectional view of FIG.
  • the porous reduction electrode 5 is directly overlaid on the electrolyte membrane 6 and bonded by thermocompression.
  • the porous reduction electrode 5 preferably has an average pore size of 1 ⁇ m or more after thermocompression bonding.
  • the porous reduction electrode 5 is, for example, copper, platinum, gold, silver, indium, palladium, gallium, nickel, tin, cadmium, porous bodies of their alloys, silver oxide, copper oxide, copper (II) oxide , nickel oxide, indium oxide, tin oxide, tungsten oxide, tungsten (VI) oxide, copper oxide, or porous metal complexes having metal ions and anionic ligands.
  • the electrolyte membrane 6 is, for example, Nafion (registered trademark), Phorblue, or Aquivion, which is a perfluorocarbon material having a carbon-fluorine skeleton.
  • step S1 in order to reduce the proton conduction resistance of the electrolyte membrane 6, the electrolyte membrane 6 is immersed in boiling nitric acid and boiling pure water.
  • step S2 the porous reduction electrode 5 is superimposed on the electrolyte membrane 6, and is thermocompression bonded by a thermocompression bonding device (for example, a hot press machine).
  • a thermocompression bonding device for example, a hot press machine.
  • the porous reduction electrode 5 is placed on the electrolyte membrane 6 and placed between two copper plates 40a and 40b, and the electrolyte membrane 6 and the porous reduction electrode 5 are placed on the copper plate. It is thermocompression-bonded together with 40a and 40b by a thermocompression bonding device.
  • the heating temperature is preferably 100°C or higher and lower than 180°C.
  • the electrolyte membrane 6 and the porous reduction electrode 5 are joined together by rapid cooling to obtain the porous electrode-supported electrolyte membrane 20 .
  • the gas-phase reduction device 100 shown in FIG. 4 is a reduction device that uses artificial photosynthesis technology to reduce carbon dioxide by light irradiation.
  • the gas-phase reduction apparatus 100 includes an oxidation tank 1 and a reduction tank 4, which are formed by dividing the internal space in the housing into two by the porous electrode-supported electrolyte membrane 20.
  • the porous electrode-supported electrolyte membrane 20 is arranged with the electrolyte membrane 6 facing the oxidation tank 1 and the reduction electrode 5 facing the reduction tank 4 .
  • the oxidation tank 1 is filled with an aqueous solution 3.
  • An oxidation electrode 2 made of a semiconductor or a metal complex is inserted into an aqueous solution 3 .
  • the oxidation electrode 2 is, for example, a compound exhibiting photoactivity and redox activity such as nitride semiconductor, titanium oxide, amorphous silicon, ruthenium complex, and rhenium complex.
  • the oxidation electrode 2 is electrically connected to the porous reduction electrode 5 by a conductor 7 .
  • the aqueous solution 3 is, for example, an aqueous potassium hydrogen carbonate solution, an aqueous sodium hydrogen carbonate solution, an aqueous potassium chloride solution, an aqueous sodium chloride solution, an aqueous sodium hydroxide solution, an aqueous potassium hydroxide solution, an aqueous rubidium hydroxide solution, or an aqueous cesium hydroxide solution.
  • Helium gas is supplied to the aqueous solution 3 from the tube 8 during the reduction reaction.
  • the reduction tank 4 is supplied with carbon dioxide from the gas inlet 10 and filled with carbon dioxide or a gas containing carbon dioxide.
  • a light source 9 is arranged so that the oxidation electrode 2 is irradiated with light.
  • the light source 9 is, for example, a xenon lamp, a simulated solar light source, a halogen lamp, a mercury lamp, and sunlight.
  • the light source 9 may be configured by combining these.
  • Example of porous electrode-supported electrolyte membrane As the porous electrode-supported electrolyte membrane 20 to be placed in the gas phase reduction apparatus 100, Example 1-6 was prepared by changing the average pore diameter or the heating temperature during the thermocompression treatment, and the gas phase reduction test described later was performed. gone. The porous electrode-supported electrolyte membranes of Examples 1-6 are described below.
  • Example 1 a copper porous body having a thickness of 0.2 mm and a porosity of 65% was used as the material of the porous reduction electrode 5 , and Nafion, which is a proton exchange membrane, was used as the material of the electrolyte membrane 6 .
  • step S1 the electrolyte membrane 6 was immersed in boiling nitric acid and boiling pure water in order to reduce the resistance of proton conduction. It was confirmed that this treatment reduced the proton conduction resistance of the electrolyte membrane 6 from 3.0 to 3.5 ⁇ .
  • step S2 the sample in which the porous reduction electrode 5 is stacked on the electrolyte membrane 6 is sandwiched between two copper plates and a hot press, and the surface of the porous reduction electrode 5 is heated at a heating temperature of 150 ° C. Pressure was applied vertically and left for 3 minutes. After that, the sample was quickly cooled and taken out to obtain a porous electrode-supported electrolyte membrane 20 in which the electrolyte membrane 6 and the porous reduction electrode 5 were joined.
  • the thickness of the porous reduction electrode 5 after thermocompression bonding was 0.14 mm, the porosity was 50%, and the average pore diameter was 1.3 ⁇ m.
  • Example 2 a porous electrode-supported electrolyte membrane 20 was produced using a copper porous body having a thickness of 0.2 mm and a porosity of 79% as the material of the porous reduction electrode 5 .
  • the porous reduction electrode 5 after thermocompression bonding had a thickness of 0.14 mm, a porosity of 70%, and an average pore diameter of 15 ⁇ m. All other conditions are the same as in Example 1.
  • Example 3 a porous electrode-supported electrolyte membrane 20 was produced using a copper porous body having a thickness of 0.2 mm and a porosity of 93% as the material of the porous reduction electrode 5 .
  • the porous reduction electrode 5 after thermocompression bonding had a thickness of 0.14 mm, a porosity of 90%, and an average pore diameter of 97 ⁇ m. All other conditions are the same as in Example 1.
  • Example 4 In Example 4, as in Example 3, a porous electrode-supported electrolyte membrane 20 was produced using a copper porous body having a thickness of 0.2 mm and a porosity of 93% as the material of the porous reduction electrode 5 .
  • the heating temperature was set to 100° C. when applying pressure with a hot press. All the conditions other than the heating temperature are the same as in Example 3.
  • Example 5 In Example 5, as in Example 3, a porous electrode-supported electrolyte membrane 20 was produced using a copper porous body having a thickness of 0.2 mm and a porosity of 93% as the material of the porous reduction electrode 5 . A heating temperature was set to 120° C. when applying pressure with a hot press. All the conditions other than the heating temperature are the same as in Example 3.
  • Example 6 a porous electrode-supported electrolyte membrane 20 was produced using a copper porous body having a thickness of 0.2 mm and a porosity of 93% as the material of the porous reduction electrode 5 .
  • a heating temperature was set to 180° C. when applying pressure with a hot press. All the conditions other than the heating temperature are the same as in Example 3.
  • the oxidation tank 1 was filled with the aqueous solution 3.
  • Aqueous solution 3 was a 1.0 mol/L potassium hydroxide aqueous solution.
  • the oxidation electrode 2 was installed in the oxidation tank 1 so as to be submerged in the aqueous solution 3.
  • a semiconductor photoelectrode manufactured as follows was used as the oxidation electrode 2 .
  • a thin film of GaN, which is an n-type semiconductor, and AlGaN were epitaxially grown in this order on a sapphire substrate, Ni was vacuum-deposited on AlGaN, and heat treatment was performed to form a NiO promoter thin film to produce a semiconductor photoelectrode.
  • a 300 W high pressure xenon lamp (wavelength of 450 nm or more was cut, illuminance 6.6 mW/cm 2 ) was used.
  • the light source 9 was fixed so that the surface of the oxidation electrode 2 on which the oxidation co-catalyst was formed became the irradiation surface.
  • the light irradiation area of the oxidation electrode 2 was set to 2.5 cm 2 .
  • He Helium
  • CO 2 carbon dioxide
  • the reduction reaction of carbon dioxide can proceed at the three-phase interface of [electrolyte membrane-copper-gas phase carbon dioxide] in the porous electrode-supported electrolyte membrane 20 .
  • the apparent area of the porous reduction electrode 5 directly supplied with carbon dioxide is about 6.25 cm 2 .
  • the light source 9 was used to uniformly irradiate the oxidation electrode 2 with light. Electrons flow between the oxidation electrode 2 and the porous reduction electrode 5 due to light irradiation.
  • the current value between the oxidation electrode 2 and the porous reduction electrode 5 during light irradiation was measured using an electrochemical measuring device (1287 type potentiogalvanostat manufactured by Solartron).
  • the gas and liquid in the oxidation tank 1 and the reduction tank 4 were sampled at arbitrary times during the light irradiation, and the reaction products were analyzed with a gas chromatograph, a liquid chromatograph, and a gas chromatograph-mass spectrometer. As a result, it was confirmed that oxygen was produced in the oxidation tank 1, and hydrogen, carbon monoxide, formic acid, methane, methanol, ethanol, and ethylene were produced in the reduction tank 4.
  • the vapor-phase reduction device 200 shown in FIG. 5 is a reduction device that uses an electrolytic reduction technique for reducing carbon dioxide by passing an electric current between an oxidation electrode and a reduction electrode.
  • the gas-phase reduction apparatus 200 includes an oxidation tank 1 and a reduction tank 4, which are formed by dividing the internal space in the housing into two by the porous electrode-supported electrolyte membrane 20.
  • the porous electrode-supported electrolyte membrane 20 is arranged with the electrolyte membrane 6 side facing the oxidation tank 1 and the reduction electrode 5 side facing the reduction tank 4 .
  • the oxidation tank 1 is filled with an aqueous solution 3.
  • An oxidation electrode 2 made of a semiconductor or a metal complex is inserted into an aqueous solution 3 .
  • the oxidation electrode 2 is, for example, platinum, gold, silver, copper, indium, or nickel.
  • the aqueous solution 3 is the same as in the vapor phase reduction apparatus 100 of FIG.
  • the reduction tank 4 is supplied with carbon dioxide from the gas inlet 10 and filled with carbon dioxide or a gas containing carbon dioxide.
  • a power supply 11 is electrically connected to the oxidation electrode 2 and the porous reduction electrode 5 by a conductor 7 .
  • Examples 7 to 12 were prepared by changing the average pore diameter or the temperature during the thermocompression bonding, and the gas phase reduction test described later was performed. rice field.
  • the porous electrode-supported electrolyte membranes of Examples 7 to 12 are described below.
  • the porous electrode-supported electrolyte membranes 20 of Examples 7-12 were prepared in the same manner as the porous electrode-supported electrolyte membranes 20 of Examples 1-6.
  • Example 7 A porous electrode-supported electrolyte membrane 20 of Example 7 was produced in the same procedure as in Example 1. The heating temperature during thermocompression bonding was 150° C., and the porous reduction electrode 5 after thermocompression bonding had a thickness of 0.14 mm, a porosity of 50%, and an average pore diameter of 1.3 ⁇ m.
  • Example 8 a porous electrode-supported electrolyte membrane 20 was produced using a copper porous body having a thickness of 0.2 mm and a porosity of 79% as the material of the porous reduction electrode 5 .
  • the porous reduction electrode 5 after thermocompression bonding had a thickness of 0.14 mm, a porosity of 70%, and an average pore diameter of 15 ⁇ m. All other conditions are the same as in Example 7.
  • Example 9 a porous electrode-supported electrolyte membrane 20 was produced using a copper porous body having a thickness of 0.2 mm and a porosity of 93% as the material of the porous reduction electrode 5 .
  • the porous reduction electrode 5 after thermocompression bonding had a thickness of 0.14 mm, a porosity of 90%, and an average pore diameter of 97 ⁇ m. All other conditions are the same as in Example 7.
  • Example 10 a porous electrode-supported electrolyte membrane 20 was produced using a copper porous body having a thickness of 0.2 mm and a porosity of 93% as the material of the porous reduction electrode 5 .
  • the heating temperature was set to 100° C. when applying pressure with a hot press. All the conditions other than the heating temperature are the same as in Example 9.
  • Example 11 In Example 11, as in Example 9, a porous electrode-supported electrolyte membrane 20 was produced using a copper porous body having a thickness of 0.2 mm and a porosity of 93% as the material of the porous reduction electrode 5 . A heating temperature was set to 120° C. when applying pressure with a hot press. All the conditions other than the heating temperature are the same as in Example 9.
  • Example 12 a porous electrode-supported electrolyte membrane 20 was produced using a copper porous body having a thickness of 0.2 mm and a porosity of 93% as the material of the porous reduction electrode 5 .
  • a heating temperature was set to 180° C. when applying pressure with a hot press. All the conditions other than the heating temperature are the same as in Example 9.
  • the oxidation tank 1 was filled with the aqueous solution 3.
  • Aqueous solution 3 was a 1.0 mol/L potassium hydroxide aqueous solution.
  • the oxidation electrode 2 was placed in the oxidation tank 1 such that about 0.55 cm 2 of its surface area was submerged in the aqueous solution 3 . Platinum (manufactured by Nilaco Corporation) was used for the oxidation electrode 2 .
  • He Helium
  • CO 2 carbon dioxide
  • the reduction reaction of carbon dioxide can proceed at the three-phase interface of [electrolyte membrane-copper-gas phase carbon dioxide] in the porous electrode-supported electrolyte membrane 20 .
  • the apparent area of the porous reduction electrode 5 directly supplied with carbon dioxide is about 6.25 cm 2 .
  • the current value between the oxidation electrode 2 and the porous reduction electrode 5 during voltage application was measured using an electrochemical measurement device.
  • the gas and liquid in the oxidation tank 1 and the reduction tank 4 were sampled at arbitrary times during voltage application, and the reaction products were analyzed with a gas chromatograph, a liquid chromatograph, and a gas chromatograph-mass spectrometer. As a result, it was confirmed that oxygen was produced in the oxidation tank 1, and hydrogen, carbon monoxide, formic acid, methane, methanol, ethanol, and ethylene were produced in the reduction tank 4.
  • Comparative Examples 1-4 having different average pore diameters or temperatures during thermocompression bonding from those of the Examples were produced, and Comparative Examples 1 and 2 were prepared as the porous electrode-supported electrolyte membrane 20 of the vapor-phase reduction apparatus 100 of FIG. , Comparative Examples 3 and 4 were arranged as the porous electrode-supported electrolyte membrane 20 of the gas phase reduction apparatus 200 of FIG. .
  • Comparative Example 1 a porous electrode-supported electrolyte membrane was produced in the same manner as in Example 1 using a copper porous body having a thickness of 0.2 mm and a porosity of 51%. After thermocompression bonding, the porous reduction electrode had a thickness of 0.14 mm, a porosity of 30%, and an average pore diameter of 0.11 ⁇ m. All other conditions are the same as in Example 1.
  • Comparative Example 3 a porous electrode-supported electrolyte membrane was produced in the same manner as in Example 7 using a copper porous body having a thickness of 0.2 mm and a porosity of 51%. After thermocompression bonding, the porous reduction electrode had a thickness of 0.14 mm, a porosity of 30%, and an average pore diameter of 0.11 ⁇ m. All other conditions are the same as in Example 7.
  • Example 1-12 and Comparative Example 1-4 [Evaluation of Examples and Comparative Examples] Next, the test results of Example 1-12 and Comparative Example 1-4 will be described. Table 1 shows the Faradaic efficiency of the carbon dioxide reduction reaction after 1 hour and the Faradaic efficiency maintenance rate of the carbon dioxide reduction reaction after 20 hours for Examples 1-12 and Comparative Example 1-4.
  • the Faraday efficiency indicates the ratio of the current value used for each reduction reaction to the current value flowing between the electrodes during light irradiation or voltage application.
  • the "charge consumed in each reduction reaction” in formula (6) can be obtained by converting the measured value of the amount of the reaction product of each reduction reaction into the charge required for the reduction reaction.
  • the amount of reaction product of each reduction reaction is A [mol]
  • the number of electrons required for the reduction reaction is Z
  • the Faraday constant is F [C/mol]
  • Faradaic efficiency maintenance rate [%] of each reduction reaction after 20 hours (Faraday efficiency of each reduction reaction after 20 hours) / (Faraday efficiency of each reduction reaction after 1 hour) x 100 (8)
  • Table 1 shows evaluation results of the diffusion coefficient of carbon dioxide in the porous electrode depending on the pore diameter. According to this, in Examples 1-5 and 7-11, which have a pore diameter of more than 1 ⁇ m, the saturation value of 6.0 ⁇ 10 ⁇ 6 m 2 s ⁇ 1 (self-diffusion coefficient) is reached. It was found to be 1.5 times.
  • porous electrode-supported electrolyte membrane 20 composed of a porous electrode having an average pore diameter of 1 ⁇ m or more at which the diffusion coefficient of carbon dioxide reaches the saturation value allows carbon dioxide to be transferred to the porous reduction electrode 5.
  • the amount of supply increased, and the efficiency of the carbon dioxide reduction reaction was improved.
  • Table 1 shows the measured proton conduction resistance of the electrolyte membrane 6 .
  • the resistance was as low as 3.0 to 3.5 ⁇ , and it was confirmed that the effect of reducing the proton conduction resistance was not lost even after the thermocompression bonding.
  • the ion conduction resistance of the electrolyte membrane 6 increased to 360 ⁇ .
  • the current value between the electrodes was remarkably low, and the amount of the reaction product fell below the lower detection limit (3%) of the evaluation system. It is considered that this is because the proton exchange group of the electrolyte membrane was decomposed by performing the thermocompression bonding treatment at a high temperature condition of 180°C.
  • the porous electrode-supported electrolyte membrane 20 of this embodiment has the electrolyte membrane 6 and the porous reduction electrode 5 directly bonded onto the electrolyte membrane 6,
  • the average pore size of the porous reduction electrode 5 is set to 1 ⁇ m or more.
  • Porous electrode-supported electrolyte membrane 20 Porous reduction electrode 5 electrolyte membrane 6

Abstract

A porous-electrode-supporting electrolyte membrane 20 according to one embodiment has an electrolyte membrane 6 and a porous redox electrode 5 joined directly on the electrolyte membrane 6. The average pore diameter of the porous redox electrode 5 is 1 μm or greater. During the step for joining the electrolyte membrane 6 and the porous redox electrode 5, swelling of the electrolyte membrane 6 is suppressed by applying pressure while heating.

Description

多孔質電極支持型電解質膜および多孔質電極支持型電解質膜の製造方法Porous electrode-supported electrolyte membrane and method for producing porous electrode-supported electrolyte membrane
　本発明は、多孔質電極支持型電解質膜および多孔質電極支持型電解質膜の製造方法に関する。 The present invention relates to a porous electrode-supported electrolyte membrane and a method for producing a porous electrode-supported electrolyte membrane.
　地球温暖化の防止およびエネルギーの安定供給という観点から、二酸化炭素を還元する技術が注目されている。二酸化炭素を還元する技術に関する装置としては、人工光合成技術を利用した還元装置と電解還元技術を利用した還元装置がある。人工光合成技術は、光触媒からなる酸化電極への光照射により、水の酸化反応と二酸化炭素の還元反応を進行させる技術である。電解還元技術は、金属からなる酸化電極と還元電極の間への電圧印加により、水の酸化反応と二酸化炭素の還元反応を進行させる技術である。太陽光を利用した人工光合成技術および再生可能エネルギー由来の電力を利用した電解還元技術は、二酸化炭素を一酸化炭素、ギ酸、エチレン等の炭化水素やメタノール、エタノール等のアルコールに再資源化することが可能な技術として注目され、近年盛んに研究されている。 Technologies that reduce carbon dioxide are attracting attention from the perspective of preventing global warming and providing a stable supply of energy. Devices related to technologies for reducing carbon dioxide include a reduction device using artificial photosynthesis technology and a reduction device using electrolytic reduction technology. Artificial photosynthesis technology is a technology that advances the oxidation reaction of water and the reduction reaction of carbon dioxide by irradiating an oxidation electrode made of a photocatalyst with light. The electrolytic reduction technique is a technique for advancing the oxidation reaction of water and the reduction reaction of carbon dioxide by applying a voltage between an oxidation electrode and a reduction electrode made of metal. Artificial photosynthesis technology using sunlight and electrolytic reduction technology using electricity derived from renewable energy can recycle carbon dioxide into hydrocarbons such as carbon monoxide, formic acid, and ethylene, and alcohols such as methanol and ethanol. has attracted attention as a technology capable of
　人工光合成技術および二酸化炭素の電解還元技術では、還元電極を水溶液に浸漬させて、水溶液中に溶解させた二酸化炭素を還元電極に供給し、還元する反応系が用いられてきた（非特許文献１，２参照）。しかし、この二酸化炭素の還元方法では、水溶液への二酸化炭素の溶解濃度および水溶液中での二酸化炭素の拡散係数に限界があり、還元電極への二酸化炭素の供給量が制限される。 In artificial photosynthesis technology and carbon dioxide electrolytic reduction technology, a reaction system has been used in which a reduction electrode is immersed in an aqueous solution, and carbon dioxide dissolved in the aqueous solution is supplied to the reduction electrode for reduction (Non-Patent Document 1 , 2). However, in this method for reducing carbon dioxide, there are limits to the concentration of carbon dioxide dissolved in the aqueous solution and the diffusion coefficient of carbon dioxide in the aqueous solution, which limits the amount of carbon dioxide supplied to the reduction electrode.
　この問題に対し、還元電極への二酸化炭素の供給量を増加させるため、還元電極に対して気相の二酸化炭素を供給する研究が進められている。非特許文献３よると、還元電極に対して気相の二酸化炭素を供給できる構造を有する反応装置を用いることで、還元電極への二酸化炭素の供給量が増大し、二酸化炭素の還元反応が促進される。 To address this problem, research is underway to supply gaseous carbon dioxide to the reduction electrode in order to increase the amount of carbon dioxide supplied to the reduction electrode. According to Non-Patent Document 3, by using a reactor having a structure that can supply gaseous carbon dioxide to the reduction electrode, the amount of carbon dioxide supplied to the reduction electrode increases, and the reduction reaction of carbon dioxide is promoted. be done.
　式（１）から式（４）に示す二酸化炭素の還元反応は、式（５）に示す水の酸化反応との組み合わせで進行する。 The reduction reactions of carbon dioxide shown in formulas (1) to (4) proceed in combination with the oxidation reaction of water shown in formula (5).
　CO2+ 2H+ + 2e- → CO + H2O　　　　　（１） 
　CO2+ 2H+ + 2e- → HCOOH 　　　　　　（２） 
　CO2+ 6H+ + 6e- → CH3OH + H2O　　　　（３） 
　CO2+ 8H+ + 8e- → CH4 + 2H2O 　　　　（４） 
　2H2O + 4h+ → O2 + 4H+　　　　　　　　（５） CO2 +2H ++ 2e- →CO+ H2O (1)
CO2 + 2H + + 2e - → HCOOH (2)
CO2 +6H ++ 6e -- > CH3OH + H2O (3)
CO2 +8H ++ 8e -- >CH4 + 2H2O ( 4 )
2H2O + 4h + → O2 + 4H + (5)
　二酸化炭素の気相還元装置では、還元槽内の水溶液を排除して気相の二酸化炭素を充填するが、気相の二酸化炭素を充填しただけではプロトン（H+）が気相中を移動できないため、電解質膜と還元電極を接合する必要がある。さらに、板状の還元電極を電解質膜に接合しただけでは気相の二酸化炭素が還元電極と電解質膜の界面に到達できないため、還元電極を多孔質にして、気相の二酸化炭素が還元電極と電解質膜の界面に到達できるようにする必要がある。この多孔質還元電極について、その気孔径が小さいと電極内での二酸化炭素の拡散抵抗が大きく、二酸化炭素の還元反応の効率が低下するという問題があった。 In the gas-phase reduction apparatus for carbon dioxide, the aqueous solution in the reduction tank is removed and the gas - phase carbon dioxide is filled. Therefore, it is necessary to bond the electrolyte membrane and the reduction electrode. Furthermore, since gaseous carbon dioxide cannot reach the interface between the reduction electrode and the electrolyte membrane only by bonding a plate-shaped reduction electrode to the electrolyte membrane, the reduction electrode is made porous so that gaseous carbon dioxide can reach the reduction electrode. It must be possible to reach the interface of the electrolyte membrane. This porous reduction electrode has a problem that if the pore diameter is small, the diffusion resistance of carbon dioxide in the electrode increases, and the efficiency of the reduction reaction of carbon dioxide decreases.
　電解質膜をプロトン交換膜として利用する際には一般的に、電解質膜のプロトン移動度を向上させるために、沸騰硝酸および沸騰純水への浸漬処理が行われる。これらの処理は、電解質膜中のプロトン交換基をH+で置換する処理であるが、この処理によって電解質膜が過剰に水分を含み膨潤した状態となってしまう。これは、電解質膜は高分子の逆ミセル構造を有しているために、膨潤し含水率が高まるためである。 When the electrolyte membrane is used as a proton exchange membrane, it is generally immersed in boiling nitric acid and boiling pure water in order to improve the proton mobility of the electrolyte membrane. These treatments are treatments for replacing the proton-exchange groups in the electrolyte membrane with H + , but this treatment causes the electrolyte membrane to be in a swollen state with excessive water content. This is because the electrolyte membrane has a polymer reverse micelle structure, which swells and increases the water content.
　この膨潤した電解質膜を多孔質還元電極に接合して気相還元装置の多孔質電極支持型電解質膜として使用すると、二酸化炭素の還元反応進行中に徐々に酸化槽の水溶液が還元電極側に浸透してきてしまう。これにより、本来気相の二酸化炭素が供給されるべきである多孔質電極の表面を水溶液が覆い、二酸化炭素の還元反応の効率が経時的に劣化するという問題があった。 When this swollen electrolyte membrane is joined to a porous reduction electrode and used as a porous electrode-supported electrolyte membrane in a gas-phase reduction apparatus, the aqueous solution in the oxidation tank gradually penetrates into the reduction electrode side while the carbon dioxide reduction reaction proceeds. It's coming. As a result, the aqueous solution covers the surface of the porous electrode to which gaseous carbon dioxide should be supplied, and the efficiency of the carbon dioxide reduction reaction deteriorates over time.
　本発明は、上記に鑑みてなされたものであり、二酸化炭素の気相還元効率を向上させることを目的とする。 The present invention has been made in view of the above, and aims to improve the gas phase reduction efficiency of carbon dioxide.
　本発明の一態様の多孔質電極支持型電解質膜は、二酸化炭素を還元する気相還元装置に用いられる多孔質電極支持型電解質膜であって、電解質膜と、前記電解質膜上に直接接合された多孔質還元電極を有し、前記多孔質還元電極の平均気孔径が１μｍ以上である。 A porous electrode-supported electrolyte membrane of one aspect of the present invention is a porous electrode-supported electrolyte membrane used in a gas-phase reduction apparatus for reducing carbon dioxide, wherein the electrolyte membrane is directly bonded to the electrolyte membrane. The porous reduction electrode has an average pore diameter of 1 μm or more.
　本発明の一態様の多孔質電極支持型電解質膜の製造方法は、二酸化炭素を還元する気相還元装置に用いられる多孔質電極支持型電解質膜の製造方法であって、電解質膜を沸騰硝酸および沸騰純水へ浸漬する工程と、前記電解質膜の表面上に多孔質還元電極を重ねて熱圧着する工程を有し、熱圧着後の前記多孔質還元電極の平均気孔径が１μｍ以上である。 A method for producing a porous electrode-supported electrolyte membrane according to one aspect of the present invention is a method for producing a porous electrode-supported electrolyte membrane used in a gas-phase reduction apparatus for reducing carbon dioxide, the electrolyte membrane comprising boiling nitric acid and boiling nitric acid. A step of immersing in boiling pure water and a step of thermally compressing a porous reduction electrode over the surface of the electrolyte membrane, wherein the average pore diameter of the porous reduction electrode after thermal compression is 1 μm or more.
　本発明によれば、二酸化炭素の気相還元効率を向上できる。 According to the present invention, the gas phase reduction efficiency of carbon dioxide can be improved.
図１は、本実施形態の多孔質電極支持型電解質膜の構成の一例を示す断面図である。FIG. 1 is a cross-sectional view showing an example of the configuration of the porous electrode-supported electrolyte membrane of this embodiment. 図２は、多孔質電極支持型電解質膜の製造方法の一例を示すフローチャートである。FIG. 2 is a flow chart showing an example of a method for producing a porous electrode-supported electrolyte membrane. 図３は、多孔質電極支持型電解質膜を製造する際に熱圧着する様子の一例を示す図である。FIG. 3 is a view showing an example of thermocompression bonding when manufacturing a porous electrode-supported electrolyte membrane. 図４は、多孔質電極支持型電解質膜を備える二酸化炭素の気相還元装置の構成の一例を示す図である。FIG. 4 is a diagram showing an example of the configuration of a gas-phase reduction apparatus for carbon dioxide provided with a porous electrode-supported electrolyte membrane. 図５は、多孔質電極支持型電解質膜を備える別の二酸化炭素の気相還元装置の構成の一例を示す図である。FIG. 5 is a diagram showing an example of the configuration of another gas-phase reduction apparatus for carbon dioxide provided with a porous electrode-supported electrolyte membrane.
　以下、本発明の実施の形態について図面を用いて説明する。本発明は、以下に記載の実施形態に限定されるものではなく、本発明の趣旨を逸脱しない範囲において変更を加えてもよい。 Embodiments of the present invention will be described below with reference to the drawings. The present invention is not limited to the embodiments described below, and modifications may be made without departing from the scope of the present invention.
　［多孔質電極支持型電解質膜の構成］
　図１の断面図を参照し、本実施形態の多孔質電極支持型電解質膜２０について説明する。 [Structure of porous electrode-supported electrolyte membrane]
A porous electrode-supported electrolyte membrane 20 of this embodiment will be described with reference to the cross-sectional view of FIG.
　図１の多孔質電極支持型電解質膜２０は、電解質膜６と、電解質膜６の表面上に直接接合された多孔質還元電極５とを備える。 The porous electrode-supported electrolyte membrane 20 in FIG.
　多孔質還元電極５は、電解質膜６に直接重ねて熱圧着されて、接合される。多孔質還元電極５は、熱圧着後の平均気孔径が１μｍ以上であるとよい。多孔質還元電極５は、例えば、銅、白金、金、銀、インジウム、パラジウム、ガリウム、ニッケル、スズ、カドミウム、それらの合金の多孔質体、または、酸化銀、酸化銅、酸化銅（ＩＩ)、酸化ニッケル、酸化インジウム、酸化スズ、酸化タングステン、酸化タングステン（ＶＩ）、酸化銅などの多孔質体、もしくは金属イオンとアニオン性配位子を有する多孔性金属錯体である。 The porous reduction electrode 5 is directly overlaid on the electrolyte membrane 6 and bonded by thermocompression. The porous reduction electrode 5 preferably has an average pore size of 1 μm or more after thermocompression bonding. The porous reduction electrode 5 is, for example, copper, platinum, gold, silver, indium, palladium, gallium, nickel, tin, cadmium, porous bodies of their alloys, silver oxide, copper oxide, copper (II) oxide , nickel oxide, indium oxide, tin oxide, tungsten oxide, tungsten (VI) oxide, copper oxide, or porous metal complexes having metal ions and anionic ligands.
　電解質膜６は、例えば、炭素－フッ素からなる骨格を持つパーフルオロカーボン材料であるナフィオン（商標登録）、フォアブルー、またはアクイヴィオンである。 The electrolyte membrane 6 is, for example, Nafion (registered trademark), Phorblue, or Aquivion, which is a perfluorocarbon material having a carbon-fluorine skeleton.
　［多孔質電極支持型電解質膜の製造方法］
　図２のフローチャートを参照し、本実施形態の多孔質電極支持型電解質膜２０の製造方法の一例について説明する。 [Method for producing porous electrode-supported electrolyte membrane]
An example of the method for manufacturing the porous electrode-supported electrolyte membrane 20 of the present embodiment will be described with reference to the flow chart of FIG.
　ステップＳ１にて、電解質膜６のプロトン伝導の抵抗を低減させるために、電解質膜６を沸騰硝酸と沸騰純水のそれぞれに浸漬する。 In step S1, in order to reduce the proton conduction resistance of the electrolyte membrane 6, the electrolyte membrane 6 is immersed in boiling nitric acid and boiling pure water.
　ステップＳ２にて、電解質膜６の上に多孔質還元電極５を重ねて熱圧着装置（例えばホットプレス機）で熱圧着する。具体的には、図３に示すように、電解質膜６の上に多孔質還元電極５を重ねて２枚の銅板４０ａ，４０ｂの間に配置し、電解質膜６と多孔質還元電極５を銅板４０ａ，４０ｂとともに熱圧着装置で熱圧着する。熱圧着の際、加熱温度を１００℃以上１８０℃未満にするとよい。 In step S2, the porous reduction electrode 5 is superimposed on the electrolyte membrane 6, and is thermocompression bonded by a thermocompression bonding device (for example, a hot press machine). Specifically, as shown in FIG. 3, the porous reduction electrode 5 is placed on the electrolyte membrane 6 and placed between two copper plates 40a and 40b, and the electrolyte membrane 6 and the porous reduction electrode 5 are placed on the copper plate. It is thermocompression-bonded together with 40a and 40b by a thermocompression bonding device. At the time of thermocompression bonding, the heating temperature is preferably 100°C or higher and lower than 180°C.
　熱圧着後、素早く冷却して、電解質膜６と多孔質還元電極５とを接合した多孔質電極支持型電解質膜２０が得られる。 After thermocompression bonding, the electrolyte membrane 6 and the porous reduction electrode 5 are joined together by rapid cooling to obtain the porous electrode-supported electrolyte membrane 20 .
　［気相還元装置（人工光合成）］
　次に、図４を参照し、本実施形態の多孔質電極支持型電解質膜２０を備えた二酸化炭素の気相還元装置１００について説明する。図４に示す気相還元装置１００は、光照射により二酸化炭素を還元する人工光合成技術を利用した還元装置である。 [Vapor-phase reduction device (artificial photosynthesis)]
Next, with reference to FIG. 4, a gas-phase reduction apparatus 100 for carbon dioxide provided with the porous electrode-supported electrolyte membrane 20 of the present embodiment will be described. The gas-phase reduction device 100 shown in FIG. 4 is a reduction device that uses artificial photosynthesis technology to reduce carbon dioxide by light irradiation.
　気相還元装置１００は、筐体内の内部空間を多孔質電極支持型電解質膜２０で二分して形成された酸化槽１と還元槽４を備える。多孔質電極支持型電解質膜２０は、電解質膜６を酸化槽１に向け、還元電極５を還元槽４に向けて配置される。 The gas-phase reduction apparatus 100 includes an oxidation tank 1 and a reduction tank 4, which are formed by dividing the internal space in the housing into two by the porous electrode-supported electrolyte membrane 20. The porous electrode-supported electrolyte membrane 20 is arranged with the electrolyte membrane 6 facing the oxidation tank 1 and the reduction electrode 5 facing the reduction tank 4 .
　酸化槽１は水溶液３で満たされる。水溶液３中に半導体または金属錯体からなる酸化電極２が挿入される。 The oxidation tank 1 is filled with an aqueous solution 3. An oxidation electrode 2 made of a semiconductor or a metal complex is inserted into an aqueous solution 3 .
　酸化電極２は、例えば、窒化物半導体、酸化チタン、アモルファスシリコン、ルテニウム錯体、レニウム錯体のような光活性およびレドックス活性を示す化合物である。酸化電極２は、導線７によって多孔質還元電極５と電気的に接続される。 The oxidation electrode 2 is, for example, a compound exhibiting photoactivity and redox activity such as nitride semiconductor, titanium oxide, amorphous silicon, ruthenium complex, and rhenium complex. The oxidation electrode 2 is electrically connected to the porous reduction electrode 5 by a conductor 7 .
　水溶液３は、例えば、炭酸水素カリウム水溶液、炭酸水素ナトリウム水溶液、塩化カリウム水溶液、塩化ナトリウム水溶液、水酸化ナトリウム水溶液、水酸化カリウム水溶液、水酸化ルビジウム水溶液、または水酸化セシウム水溶液である。還元反応中、水溶液３には、チューブ８からヘリウムガスが供給される。 The aqueous solution 3 is, for example, an aqueous potassium hydrogen carbonate solution, an aqueous sodium hydrogen carbonate solution, an aqueous potassium chloride solution, an aqueous sodium chloride solution, an aqueous sodium hydroxide solution, an aqueous potassium hydroxide solution, an aqueous rubidium hydroxide solution, or an aqueous cesium hydroxide solution. Helium gas is supplied to the aqueous solution 3 from the tube 8 during the reduction reaction.
　還元槽４は、気体入力口１０から二酸化炭素が供給されて、二酸化炭素または二酸化炭素を含む気体で満たされる。 The reduction tank 4 is supplied with carbon dioxide from the gas inlet 10 and filled with carbon dioxide or a gas containing carbon dioxide.
　光源９が、酸化電極２に光が照射されるように配置される。光源９は、例えば、キセノンランプ、擬似太陽光源、ハロゲンランプ、水銀ランプ、および太陽光である。光源９は、これら組み合わせて構成してもよい。 A light source 9 is arranged so that the oxidation electrode 2 is irradiated with light. The light source 9 is, for example, a xenon lamp, a simulated solar light source, a halogen lamp, a mercury lamp, and sunlight. The light source 9 may be configured by combining these.
　［多孔質電極支持型電解質膜の実施例］
　上記の気相還元装置１００に配置する多孔質電極支持型電解質膜２０として、平均気孔径または熱圧着処理時の加熱温度を変えた実施例１－６を作製し、後述の気相還元試験を行った。以下、実施例１－６の多孔質電極支持型電解質膜について説明する。 [Example of porous electrode-supported electrolyte membrane]
As the porous electrode-supported electrolyte membrane 20 to be placed in the gas phase reduction apparatus 100, Example 1-6 was prepared by changing the average pore diameter or the heating temperature during the thermocompression treatment, and the gas phase reduction test described later was performed. gone. The porous electrode-supported electrolyte membranes of Examples 1-6 are described below.
　＜実施例１＞
　実施例１では、多孔質還元電極５の材料として厚み０．２ｍｍ、気孔率６５％の銅多孔質体を用い、電解質膜６の材料としてプロトン交換膜であるナフィオンを用いた。 <Example 1>
In Example 1, a copper porous body having a thickness of 0.2 mm and a porosity of 65% was used as the material of the porous reduction electrode 5 , and Nafion, which is a proton exchange membrane, was used as the material of the electrolyte membrane 6 .
　ステップＳ１にて、プロトン伝導の抵抗を低減させるために、電解質膜６を沸騰硝酸と沸騰純水にそれぞれ浸漬した。この処理により電解質膜６のプロトン伝導の抵抗が３．０から３．５Ωまで低減されることを確認した。 In step S1, the electrolyte membrane 6 was immersed in boiling nitric acid and boiling pure water in order to reduce the resistance of proton conduction. It was confirmed that this treatment reduced the proton conduction resistance of the electrolyte membrane 6 from 3.0 to 3.5Ω.
　ステップＳ２にて、電解質膜６の上に多孔質還元電極５を重ねたサンプルを２枚の銅板とホットプレス機で挟み、加熱温度１５０℃の条件で、多孔質還元電極５の表面に対して垂直方向に圧力を加えて３分放置した。その後、サンプルを素早く冷却して取り出し、電解質膜６と多孔質還元電極５が接合した多孔質電極支持型電解質膜２０を得た。 In step S2, the sample in which the porous reduction electrode 5 is stacked on the electrolyte membrane 6 is sandwiched between two copper plates and a hot press, and the surface of the porous reduction electrode 5 is heated at a heating temperature of 150 ° C. Pressure was applied vertically and left for 3 minutes. After that, the sample was quickly cooled and taken out to obtain a porous electrode-supported electrolyte membrane 20 in which the electrolyte membrane 6 and the porous reduction electrode 5 were joined.
　熱圧着後の多孔質還元電極５の厚みは０．１４ｍｍ、気孔率は５０％、平均気孔径は１．３μｍであった。 The thickness of the porous reduction electrode 5 after thermocompression bonding was 0.14 mm, the porosity was 50%, and the average pore diameter was 1.3 μm.
　＜実施例２＞
　実施例２では、多孔質還元電極５の材料として厚み０．２ｍｍ、気孔率７９％の銅多孔質体を用いて多孔質電極支持型電解質膜２０を作製した。熱圧着後の多孔質還元電極５の厚みは０．１４ｍｍ、気孔率は７０％、平均気孔径は１５μｍであった。それ以外の条件は全て実施例１と同様である。 <Example 2>
In Example 2, a porous electrode-supported electrolyte membrane 20 was produced using a copper porous body having a thickness of 0.2 mm and a porosity of 79% as the material of the porous reduction electrode 5 . The porous reduction electrode 5 after thermocompression bonding had a thickness of 0.14 mm, a porosity of 70%, and an average pore diameter of 15 μm. All other conditions are the same as in Example 1.
　＜実施例３＞
　実施例３では、多孔質還元電極５の材料として厚み０．２ｍｍ、気孔率９３％の銅多孔質体を用いて多孔質電極支持型電解質膜２０を作製した。熱圧着後の多孔質還元電極５の厚みは０．１４ｍｍ、気孔率は９０％、平均気孔径は９７μｍであった。それ以外の条件は全て実施例１と同様である。 <Example 3>
In Example 3, a porous electrode-supported electrolyte membrane 20 was produced using a copper porous body having a thickness of 0.2 mm and a porosity of 93% as the material of the porous reduction electrode 5 . The porous reduction electrode 5 after thermocompression bonding had a thickness of 0.14 mm, a porosity of 90%, and an average pore diameter of 97 μm. All other conditions are the same as in Example 1.
　＜実施例４＞
　実施例４では、実施例３と同様に、多孔質還元電極５の材料として厚み０．２ｍｍ、気孔率９３％の銅多孔質体を用いて多孔質電極支持型電解質膜２０を作製した。ホットプレス機で圧力を加える際の加熱温度を１００℃とした。加熱温度以外の条件は全て実施例３と同様である。 <Example 4>
In Example 4, as in Example 3, a porous electrode-supported electrolyte membrane 20 was produced using a copper porous body having a thickness of 0.2 mm and a porosity of 93% as the material of the porous reduction electrode 5 . The heating temperature was set to 100° C. when applying pressure with a hot press. All the conditions other than the heating temperature are the same as in Example 3.
　＜実施例５＞
　実施例５では、実施例３と同様に、多孔質還元電極５の材料として厚み０．２ｍｍ、気孔率９３％の銅多孔質体を用いて多孔質電極支持型電解質膜２０を作製した。ホットプレス機で圧力を加える際の加熱温度を１２０℃とした。加熱温度以外の条件は全て実施例３と同様である。 <Example 5>
In Example 5, as in Example 3, a porous electrode-supported electrolyte membrane 20 was produced using a copper porous body having a thickness of 0.2 mm and a porosity of 93% as the material of the porous reduction electrode 5 . A heating temperature was set to 120° C. when applying pressure with a hot press. All the conditions other than the heating temperature are the same as in Example 3.
　＜実施例６＞
　実施例６では、実施例３と同様に、多孔質還元電極５の材料として厚み０．２ｍｍ、気孔率９３％の銅多孔質体を用いて多孔質電極支持型電解質膜２０を作製した。ホットプレス機で圧力を加える際の加熱温度を１８０℃とした。加熱温度以外の条件は全て実施例３と同様である。 <Example 6>
In Example 6, as in Example 3, a porous electrode-supported electrolyte membrane 20 was produced using a copper porous body having a thickness of 0.2 mm and a porosity of 93% as the material of the porous reduction electrode 5 . A heating temperature was set to 180° C. when applying pressure with a hot press. All the conditions other than the heating temperature are the same as in Example 3.
　［電気化学測定およびガス・液体生成量測定］
　実施例１－６の多孔質電極支持型電解質膜２０のそれぞれを図４の気相還元装置１００に取り付けて以下の還元反応試験を行った。 [Electrochemical measurement and measurement of gas/liquid production]
Each of the porous electrode-supported electrolyte membranes 20 of Examples 1-6 was attached to the gas phase reduction apparatus 100 of FIG. 4, and the following reduction reaction test was performed.
　酸化槽１を水溶液３で満たした。水溶液３は、１．０ｍｏｌ／Ｌの水酸化カリウム水溶液とした。 The oxidation tank 1 was filled with the aqueous solution 3. Aqueous solution 3 was a 1.0 mol/L potassium hydroxide aqueous solution.
　酸化電極２を水溶液３に浸水するように酸化槽１内に設置した。酸化電極２には、次のように作製した半導体光電極を用いた。サファイア基板上にｎ型半導体であるＧａＮの薄膜とＡｌＧａＮを順にエピタキシャル成長させ、ＡｌＧａＮ上にＮｉを真空蒸着して熱処理を行ってＮｉＯの助触媒薄膜を形成した半導体光電極を作製した。 The oxidation electrode 2 was installed in the oxidation tank 1 so as to be submerged in the aqueous solution 3. A semiconductor photoelectrode manufactured as follows was used as the oxidation electrode 2 . A thin film of GaN, which is an n-type semiconductor, and AlGaN were epitaxially grown in this order on a sapphire substrate, Ni was vacuum-deposited on AlGaN, and heat treatment was performed to form a NiO promoter thin film to produce a semiconductor photoelectrode.
　光源９には、３００Ｗの高圧キセノンランプ（波長４５０ｎｍ以上をカット、照度６．６ｍＷ／ｃｍ２）を用いた。光源９は、酸化電極２の酸化助触媒が形成されている面が照射面となるように固定した。酸化電極２の光照射面積を２．５ｃｍ２とした。 As the light source 9, a 300 W high pressure xenon lamp (wavelength of 450 nm or more was cut, illuminance 6.6 mW/cm 2 ) was used. The light source 9 was fixed so that the surface of the oxidation electrode 2 on which the oxidation co-catalyst was formed became the irradiation surface. The light irradiation area of the oxidation electrode 2 was set to 2.5 cm 2 .
　酸化槽１に対してはチューブ８からヘリウム（Ｈｅ）を、還元槽４に対しては気体入力口１０から二酸化炭素（ＣＯ２）を、それぞれ流量５ｍｌ／ｍｉｎかつ圧力０．１８ＭＰａで流した。この系では、多孔質電極支持型電解質膜２０内の［電解質膜－銅－気相の二酸化炭素］からなる三相界面において、二酸化炭素の還元反応を進行させることができる。多孔質還元電極５の二酸化炭素が直接供給される見かけ面積は、約６．２５ｃｍ２である。 Helium (He) was supplied to the oxidation tank 1 from the tube 8 and carbon dioxide (CO 2 ) was supplied to the reduction tank 4 from the gas inlet 10 at a flow rate of 5 ml/min and a pressure of 0.18 MPa. In this system, the reduction reaction of carbon dioxide can proceed at the three-phase interface of [electrolyte membrane-copper-gas phase carbon dioxide] in the porous electrode-supported electrolyte membrane 20 . The apparent area of the porous reduction electrode 5 directly supplied with carbon dioxide is about 6.25 cm 2 .
　酸化槽１および還元槽４をヘリウムと二酸化炭素で十分に置換した後、光源９を用いて酸化電極２に均一に光を照射した。光照射により、酸化電極２と多孔質還元電極５との間に電子が流れる。 After sufficiently replacing the oxidation tank 1 and the reduction tank 4 with helium and carbon dioxide, the light source 9 was used to uniformly irradiate the oxidation electrode 2 with light. Electrons flow between the oxidation electrode 2 and the porous reduction electrode 5 due to light irradiation.
　光照射時の酸化電極２と多孔質還元電極５との間の電流値を、電気化学測定装置（Solartron社製、1287型ポテンショガルバノスタット）を用いて測定した。また、光照射中任意の時間に、酸化槽１および還元槽４内のガスと液体を採取し、ガスクロマトグラフ、液体クロマトグラフ、およびガスクロマトグラフ質量分析計にて反応生成物を分析した。その結果、酸化槽１内では酸素が、還元槽４内では、水素、一酸化炭素、ギ酸、メタン、メタノール、エタノール、エチレンが生成していることを確認した。 The current value between the oxidation electrode 2 and the porous reduction electrode 5 during light irradiation was measured using an electrochemical measuring device (1287 type potentiogalvanostat manufactured by Solartron). In addition, the gas and liquid in the oxidation tank 1 and the reduction tank 4 were sampled at arbitrary times during the light irradiation, and the reaction products were analyzed with a gas chromatograph, a liquid chromatograph, and a gas chromatograph-mass spectrometer. As a result, it was confirmed that oxygen was produced in the oxidation tank 1, and hydrogen, carbon monoxide, formic acid, methane, methanol, ethanol, and ethylene were produced in the reduction tank 4.
　なお、実施例１－６の試験結果は、下記の実施例７－１４および比較対象例１－４の試験結果とともに後述する。 The test results of Examples 1-6 will be described later together with the test results of Examples 7-14 and Comparative Examples 1-4 below.
　［気相還元装置（電解還元）］
　次に、図５を参照し、本実施形態の多孔質電極支持型電解質膜２０を備えた二酸化炭素の気相還元装置２００について説明する。図５に示す気相還元装置２００は、酸化電極と還元電極との間に電流を流して二酸化炭素を還元する電解還元技術を利用した還元装置である。 [Vapor phase reduction device (electrolytic reduction)]
Next, with reference to FIG. 5, a carbon dioxide vapor-phase reduction apparatus 200 including the porous electrode-supported electrolyte membrane 20 of the present embodiment will be described. The vapor-phase reduction device 200 shown in FIG. 5 is a reduction device that uses an electrolytic reduction technique for reducing carbon dioxide by passing an electric current between an oxidation electrode and a reduction electrode.
　気相還元装置２００は、筐体内の内部空間を多孔質電極支持型電解質膜２０で二分して形成された酸化槽１と還元槽４を備える。多孔質電極支持型電解質膜２０は、電解質膜６側を酸化槽１に向け、還元電極５側を還元槽４に向けて配置される。 The gas-phase reduction apparatus 200 includes an oxidation tank 1 and a reduction tank 4, which are formed by dividing the internal space in the housing into two by the porous electrode-supported electrolyte membrane 20. The porous electrode-supported electrolyte membrane 20 is arranged with the electrolyte membrane 6 side facing the oxidation tank 1 and the reduction electrode 5 side facing the reduction tank 4 .
　酸化槽１は水溶液３で満たされる。水溶液３中に半導体または金属錯体からなる酸化電極２が挿入される。 The oxidation tank 1 is filled with an aqueous solution 3. An oxidation electrode 2 made of a semiconductor or a metal complex is inserted into an aqueous solution 3 .
　酸化電極２は、例えば、白金、金、銀、銅、インジウム、ニッケルである。 The oxidation electrode 2 is, for example, platinum, gold, silver, copper, indium, or nickel.
　水溶液３は、図４の気相還元装置１００と同様である。 The aqueous solution 3 is the same as in the vapor phase reduction apparatus 100 of FIG.
　還元槽４は、気体入力口１０から二酸化炭素が供給されて、二酸化炭素または二酸化炭素を含む気体で満たされる。 The reduction tank 4 is supplied with carbon dioxide from the gas inlet 10 and filled with carbon dioxide or a gas containing carbon dioxide.
　電源１１が、導線７によって酸化電極２と多孔質還元電極５とに電気的に接続される。 A power supply 11 is electrically connected to the oxidation electrode 2 and the porous reduction electrode 5 by a conductor 7 .
　［多孔質電極支持型電解質膜の実施例］
　上記の気相還元装置２００に配置する多孔質電極支持型電解質膜２０として、平均気孔径または熱圧着処理時の温度を変えた実施例７－１２を作製し、後述の気相還元試験を行った。以下、実施例７－１２の多孔質電極支持型電解質膜について説明する。なお、実施例７－１２の多孔質電極支持型電解質膜２０は、実施例１－６の多孔質電極支持型電解質膜２０と同様に作製した。 [Example of porous electrode-supported electrolyte membrane]
As the porous electrode-supported electrolyte membranes 20 to be placed in the gas phase reduction apparatus 200, Examples 7 to 12 were prepared by changing the average pore diameter or the temperature during the thermocompression bonding, and the gas phase reduction test described later was performed. rice field. The porous electrode-supported electrolyte membranes of Examples 7 to 12 are described below. The porous electrode-supported electrolyte membranes 20 of Examples 7-12 were prepared in the same manner as the porous electrode-supported electrolyte membranes 20 of Examples 1-6.
　＜実施例７＞
　実施例７の多孔質電極支持型電解質膜２０は、実施例１と同様の手順で作製した。熱圧着時の加熱温度は１５０℃であり、熱圧着後の多孔質還元電極５の厚みは０．１４ｍｍ、気孔率は５０％、平均気孔径は１．３μｍであった。 <Example 7>
A porous electrode-supported electrolyte membrane 20 of Example 7 was produced in the same procedure as in Example 1. The heating temperature during thermocompression bonding was 150° C., and the porous reduction electrode 5 after thermocompression bonding had a thickness of 0.14 mm, a porosity of 50%, and an average pore diameter of 1.3 μm.
　＜実施例８＞
　実施例８では、多孔質還元電極５の材料として厚み０．２ｍｍ、気孔率７９％の銅多孔質体を用いて多孔質電極支持型電解質膜２０を作製した。熱圧着後の多孔質還元電極５の厚みは０．１４ｍｍ、気孔率は７０％、平均気孔径は１５μｍであった。それ以外の条件は全て実施例７と同様である。 <Example 8>
In Example 8, a porous electrode-supported electrolyte membrane 20 was produced using a copper porous body having a thickness of 0.2 mm and a porosity of 79% as the material of the porous reduction electrode 5 . The porous reduction electrode 5 after thermocompression bonding had a thickness of 0.14 mm, a porosity of 70%, and an average pore diameter of 15 μm. All other conditions are the same as in Example 7.
　＜実施例９＞
　実施例９では、多孔質還元電極５の材料として厚み０．２ｍｍ、気孔率９３％の銅多孔質体を用いて多孔質電極支持型電解質膜２０を作製した。熱圧着後の多孔質還元電極５の厚みは０．１４ｍｍ、気孔率は９０％、平均気孔径は９７μｍであった。それ以外の条件は全て実施例７と同様である。 <Example 9>
In Example 9, a porous electrode-supported electrolyte membrane 20 was produced using a copper porous body having a thickness of 0.2 mm and a porosity of 93% as the material of the porous reduction electrode 5 . The porous reduction electrode 5 after thermocompression bonding had a thickness of 0.14 mm, a porosity of 90%, and an average pore diameter of 97 μm. All other conditions are the same as in Example 7.
　＜実施例１０＞
　実施例１０では、実施例９と同様に、多孔質還元電極５の材料として厚み０．２ｍｍ、気孔率９３％の銅多孔質体を用いて多孔質電極支持型電解質膜２０を作製した。ホットプレス機で圧力を加える際の加熱温度を１００℃とした。加熱温度以外の条件は全て実施例９と同様である。 <Example 10>
In Example 10, as in Example 9, a porous electrode-supported electrolyte membrane 20 was produced using a copper porous body having a thickness of 0.2 mm and a porosity of 93% as the material of the porous reduction electrode 5 . The heating temperature was set to 100° C. when applying pressure with a hot press. All the conditions other than the heating temperature are the same as in Example 9.
　＜実施例１１＞
　実施例１１では、実施例９と同様に、多孔質還元電極５の材料として厚み０．２ｍｍ、気孔率９３％の銅多孔質体を用いて多孔質電極支持型電解質膜２０を作製した。ホットプレス機で圧力を加える際の加熱温度を１２０℃とした。加熱温度以外の条件は全て実施例９と同様である。 <Example 11>
In Example 11, as in Example 9, a porous electrode-supported electrolyte membrane 20 was produced using a copper porous body having a thickness of 0.2 mm and a porosity of 93% as the material of the porous reduction electrode 5 . A heating temperature was set to 120° C. when applying pressure with a hot press. All the conditions other than the heating temperature are the same as in Example 9.
　＜実施例１２＞
　実施例１２では、実施例９と同様に、多孔質還元電極５の材料として厚み０．２ｍｍ、気孔率９３％の銅多孔質体を用いて多孔質電極支持型電解質膜２０を作製した。ホットプレス機で圧力を加える際の加熱温度を１８０℃とした。加熱温度以外の条件は全て実施例９と同様である。 <Example 12>
In Example 12, as in Example 9, a porous electrode-supported electrolyte membrane 20 was produced using a copper porous body having a thickness of 0.2 mm and a porosity of 93% as the material of the porous reduction electrode 5 . A heating temperature was set to 180° C. when applying pressure with a hot press. All the conditions other than the heating temperature are the same as in Example 9.
　［電気化学測定およびガス・液体生成量測定］
　実施例７－１２の多孔質電極支持型電解質膜２０のそれぞれを図５の気相還元装置２００に取り付けて以下の還元反応試験を行った。 [Electrochemical measurement and measurement of gas/liquid production]
Each of the porous electrode-supported electrolyte membranes 20 of Examples 7 to 12 was attached to the vapor phase reduction apparatus 200 of FIG. 5, and the following reduction reaction test was performed.
　酸化槽１を水溶液３で満たした。水溶液３は、１．０ｍｏｌ／Ｌの水酸化カリウム水溶液とした。 The oxidation tank 1 was filled with the aqueous solution 3. Aqueous solution 3 was a 1.0 mol/L potassium hydroxide aqueous solution.
　酸化電極２を表面積の約０．５５ｃｍ２が水溶液３に浸水するように酸化槽１に設置した。酸化電極２には白金（ニラコ社製）を用いた。 The oxidation electrode 2 was placed in the oxidation tank 1 such that about 0.55 cm 2 of its surface area was submerged in the aqueous solution 3 . Platinum (manufactured by Nilaco Corporation) was used for the oxidation electrode 2 .
　酸化槽１に対してはチューブ８からヘリウム（Ｈｅ）を、還元槽４に対しては気体入力口１０から二酸化炭素（ＣＯ２）を、それぞれ流量５ｍｌ／ｍｉｎかつ圧力０．１８ＭＰａで流した。この系では、多孔質電極支持型電解質膜２０内の［電解質膜－銅－気相の二酸化炭素］からなる三相界面において、二酸化炭素の還元反応を進行させることができる。多孔質還元電極５の二酸化炭素が直接供給される見かけ面積は、約６．２５ｃｍ２である。 Helium (He) was supplied to the oxidation tank 1 from the tube 8 and carbon dioxide (CO 2 ) was supplied to the reduction tank 4 from the gas inlet 10 at a flow rate of 5 ml/min and a pressure of 0.18 MPa. In this system, the reduction reaction of carbon dioxide can proceed at the three-phase interface of [electrolyte membrane-copper-gas phase carbon dioxide] in the porous electrode-supported electrolyte membrane 20 . The apparent area of the porous reduction electrode 5 directly supplied with carbon dioxide is about 6.25 cm 2 .
　酸化槽１および還元槽４をヘリウムと二酸化炭素で十分に置換した後、電源１１により電圧２．０Ｖを印加して酸化電極２と多孔質還元電極５との間に電子を流した。 After sufficiently replacing the oxidation tank 1 and the reduction tank 4 with helium and carbon dioxide, a voltage of 2.0 V was applied from the power supply 11 to allow electrons to flow between the oxidation electrode 2 and the porous reduction electrode 5 .
　電圧印加時の酸化電極２と多孔質還元電極５との間の電流値を、電気化学測定装置を用いて測定した。 The current value between the oxidation electrode 2 and the porous reduction electrode 5 during voltage application was measured using an electrochemical measurement device.
　また、電圧印加時の任意の時間に、酸化槽１および還元槽４内のガスと液体を採取し、ガスクロマトグラフ、液体クロマトグラフ、およびガスクロマトグラフ質量分析計にて反応生成物を分析した。その結果、酸化槽１内では酸素が、還元槽４内では、水素、一酸化炭素、ギ酸、メタン、メタノール、エタノール、エチレンが生成していることを確認した。 In addition, the gas and liquid in the oxidation tank 1 and the reduction tank 4 were sampled at arbitrary times during voltage application, and the reaction products were analyzed with a gas chromatograph, a liquid chromatograph, and a gas chromatograph-mass spectrometer. As a result, it was confirmed that oxygen was produced in the oxidation tank 1, and hydrogen, carbon monoxide, formic acid, methane, methanol, ethanol, and ethylene were produced in the reduction tank 4.
　［比較対象例］
　実施例とは平均気孔径または熱圧着処理時の温度が異なる比較対象例１－４を作製し、比較対象例１，２を図４の気相還元装置１００の多孔質電極支持型電解質膜２０として配置し、比較対象例３，４を図５の気相還元装置２００の多孔質電極支持型電解質膜２０として配置して実施例１－６および実施例７－１２と同様の試験を行った。 [Comparison example]
Comparative Examples 1-4 having different average pore diameters or temperatures during thermocompression bonding from those of the Examples were produced, and Comparative Examples 1 and 2 were prepared as the porous electrode-supported electrolyte membrane 20 of the vapor-phase reduction apparatus 100 of FIG. , Comparative Examples 3 and 4 were arranged as the porous electrode-supported electrolyte membrane 20 of the gas phase reduction apparatus 200 of FIG. .
　＜比較対象例１＞
　比較対象例１では、厚み０．２ｍｍ、気孔率５１％の銅多孔質体を用いて実施例１と同様に多孔質電極支持型電解質膜を作製した。熱圧着後の多孔質還元電極の厚みは０．１４ｍｍ、気孔率は３０％、平均気孔径は０．１１μｍであった。それ以外の条件は全て実施例１と同様である。 <Comparison example 1>
In Comparative Example 1, a porous electrode-supported electrolyte membrane was produced in the same manner as in Example 1 using a copper porous body having a thickness of 0.2 mm and a porosity of 51%. After thermocompression bonding, the porous reduction electrode had a thickness of 0.14 mm, a porosity of 30%, and an average pore diameter of 0.11 μm. All other conditions are the same as in Example 1.
　＜比較対象例２＞
　比較対象例２では、熱圧着時の加熱温度を８０℃とした。加熱温度以外の条件は全て実施例３と同様である。 <Comparative example 2>
In Comparative Example 2, the heating temperature during thermocompression bonding was set to 80°C. All the conditions other than the heating temperature are the same as in Example 3.
　＜比較対象例３＞
　比較対象例３では、厚み０．２ｍｍ、気孔率５１％の銅多孔質体を用いて実施例７と同様に多孔質電極支持型電解質膜を作製した。熱圧着後の多孔質還元電極の厚みは０．１４ｍｍ、気孔率は３０％、平均気孔径は０．１１μｍであった。それ以外の条件は全て実施例７と同様である。 <Comparative example 3>
In Comparative Example 3, a porous electrode-supported electrolyte membrane was produced in the same manner as in Example 7 using a copper porous body having a thickness of 0.2 mm and a porosity of 51%. After thermocompression bonding, the porous reduction electrode had a thickness of 0.14 mm, a porosity of 30%, and an average pore diameter of 0.11 μm. All other conditions are the same as in Example 7.
　＜比較対象例４＞
　比較対象例４では、熱圧着時の加熱温度を８０℃とした。加熱温度以外の条件は全て実施例９と同様である。 <Comparative example 4>
In Comparative Example 4, the heating temperature during thermocompression bonding was set to 80°C. All the conditions other than the heating temperature are the same as in Example 9.
　［実施例と比較対象例の評価］
　次に、実施例１－１２と比較対象例１－４の試験結果について説明する。表１に、実施例１－１２および比較対象例１－４に関して、１時間後の二酸化炭素還元反応のファラデー効率および２０時間後の二酸化炭素還元反応のファラデー効率維持率を示す。 [Evaluation of Examples and Comparative Examples]
Next, the test results of Example 1-12 and Comparative Example 1-4 will be described. Table 1 shows the Faradaic efficiency of the carbon dioxide reduction reaction after 1 hour and the Faradaic efficiency maintenance rate of the carbon dioxide reduction reaction after 20 hours for Examples 1-12 and Comparative Example 1-4.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
　ファラデー効率とは、式（６）に示すように、光照射時または電圧印加時に電極間に流れた電流値に対して、各還元反応に使われた電流値の割合を示すものである。 The Faraday efficiency, as shown in formula (6), indicates the ratio of the current value used for each reduction reaction to the current value flowing between the electrodes during light irradiation or voltage application.
　各還元反応のファラデー効率［％］＝（各還元反応に消費された電荷）／（酸化電極－還元電極間を流れた電荷）×１００　　　　　（６） 　Faraday efficiency [%] of each reduction reaction = (charge consumed in each reduction reaction)/(charge flowing between oxidation electrode and reduction electrode) x 100 (6)
　ここで、式（６）の「各還元反応に消費された電荷」は、各還元反応の反応生成物量の測定値を、その還元反応に必要な電荷に換算することで求めることができる。各還元反応の反応生成物量をＡ［ｍｏｌ］、還元反応に必要な電子数をＺ、ファラデー定数をＦ［Ｃ／ｍｏｌ］としたとき、式（７）を用いて算出した。 Here, the "charge consumed in each reduction reaction" in formula (6) can be obtained by converting the measured value of the amount of the reaction product of each reduction reaction into the charge required for the reduction reaction. When the amount of reaction product of each reduction reaction is A [mol], the number of electrons required for the reduction reaction is Z, and the Faraday constant is F [C/mol], it was calculated using Equation (7).
　各還元反応に消費された電荷［Ｃ］＝Ａ×Ｚ×Ｆ　　　　　（７） Charge consumed for each reduction reaction [C] = A x Z x F (7)
　また、２０時間後の各還元反応のファラデー効率維持率は下記の式（８）の通り定義し、算出した。 In addition, the Faraday efficiency maintenance rate of each reduction reaction after 20 hours was defined and calculated according to the following formula (8).
　２０時間後の各還元反応のファラデー効率維持率［％］＝（２０時間後の各還元反応のファラデー効率）／（１時間後の各還元反応のファラデー効率）×１００　　　（８） Faradaic efficiency maintenance rate [%] of each reduction reaction after 20 hours = (Faraday efficiency of each reduction reaction after 20 hours) / (Faraday efficiency of each reduction reaction after 1 hour) x 100 (8)
　１時間後の二酸化炭素還元反応のファラデー効率について、実施例１－５と比較対象例１、実施例７－１１と比較対象例３をそれぞれ比較すると、実施例１－５，７－１１の方が比較対象例１，３よりも１時間後の二酸化炭素還元反応のファラデー効率が高かった。 Regarding the Faradaic efficiency of the carbon dioxide reduction reaction after 1 hour, when comparing Example 1-5 with Comparative Example 1 and Example 7-11 with Comparative Example 3, Examples 1-5 and 7-11 are better. However, the Faradaic efficiency of the carbon dioxide reduction reaction after 1 hour was higher than that of Comparative Examples 1 and 3.
　表１には、気孔径に依存する多孔質電極内での二酸化炭素の拡散係数の評価結果を示している。これによると、気孔径１μｍを超える実施例１－５，７－１１では、飽和値６．０ｘ１０－６ｍ２ｓ－１（自己拡散係数）に達しており、比較対象例１、３のおよそ１．５倍であることが分かった。 Table 1 shows evaluation results of the diffusion coefficient of carbon dioxide in the porous electrode depending on the pore diameter. According to this, in Examples 1-5 and 7-11, which have a pore diameter of more than 1 μm, the saturation value of 6.0×10 −6 m 2 s −1 (self-diffusion coefficient) is reached. It was found to be 1.5 times.
　これらのことから、二酸化炭素の拡散係数が飽和値になる平均気孔径１μｍ以上の多孔質電極で構成される多孔質電極支持型電解質膜２０を用いることで、多孔質還元電極５への二酸化炭素供給量が増加し、二酸化炭素還元反応の効率向上を実現できた。 For these reasons, the use of the porous electrode-supported electrolyte membrane 20 composed of a porous electrode having an average pore diameter of 1 μm or more at which the diffusion coefficient of carbon dioxide reaches the saturation value allows carbon dioxide to be transferred to the porous reduction electrode 5. The amount of supply increased, and the efficiency of the carbon dioxide reduction reaction was improved.
　２０時間後の二酸化炭素還元反応のファラデー効率維持率について、実施例１－５と比較対象例２、実施例７－１１と比較対象例４をそれぞれ比較すると、実施例１－５，７－１１の方が比較対象例２，４よりも２０時間後の二酸化炭素還元反応のファラデー効率維持率が高かった。 Regarding the Faraday efficiency maintenance rate of the carbon dioxide reduction reaction after 20 hours, comparing Example 1-5 with Comparative Example 2 and Example 7-11 with Comparative Example 4, Examples 1-5 and 7-11 Compared to Comparative Examples 2 and 4, the Faraday efficiency retention rate of the carbon dioxide reduction reaction after 20 hours was higher.
　実施例１－５，７－１１では２０時間後の電極表面には目視で確認できるほどの液体の付着はなかった。一方で、比較対象例２，４では２０時間後の電極表面に液体が数百μＬ付着しており、電極表面に直接的に気相の二酸化炭素を供給できなくなったことでファラデー効率維持率が低くなったことが分かった。電極表面に付着した液体は主に、二酸化炭素還元反応進行の有無にかかわらず酸化槽１から電解質膜６を介して浸透してくる水溶液であることを確認した。これは、電解質膜６が過剰な水分をため込んだ膨潤状態になり、酸化槽１内の水溶液３が浸透したことが原因と考えられる。一方で、実施例１－５と実施例７－１１では、熱圧着を１００℃以上の温度条件で実施することで、電解質膜中に含まれる水分を気化させることができた。これにより、電解質膜を介した水溶液浸透が抑制されて二酸化炭素還元反応の維持率が向上したと考えらえる。 In Examples 1-5 and 7-11, no liquid adhered to the electrode surface after 20 hours so that it could be visually confirmed. On the other hand, in Comparative Examples 2 and 4, several hundred μL of liquid adhered to the electrode surface after 20 hours, and gaseous carbon dioxide could not be supplied directly to the electrode surface, so the Faraday efficiency maintenance rate decreased. found to be lower. It was confirmed that the liquid adhering to the electrode surface was mainly an aqueous solution that permeated through the electrolyte membrane 6 from the oxidation tank 1 regardless of the progress of the carbon dioxide reduction reaction. The reason for this is considered to be that the electrolyte membrane 6 is in a swollen state with excess water accumulated, and the aqueous solution 3 in the oxidation tank 1 permeates. On the other hand, in Examples 1-5 and 7-11, it was possible to evaporate the moisture contained in the electrolyte membrane by performing the thermocompression bonding at a temperature of 100° C. or higher. Presumably, this inhibited the permeation of the aqueous solution through the electrolyte membrane and improved the maintenance rate of the carbon dioxide reduction reaction.
　さらに、表１には、測定した電解質膜６のプロトン伝導の抵抗を示している。実施例１－５と実施例７－１１では３．０～３．５Ωと低抵抗であり、熱圧着後もプロトン伝導の抵抗低減の効果が失われていないことが確認できた。一方で、実施例６，１２では、電解質膜６のイオン伝導の抵抗が３６０Ωに増大していた。これにより、電極間の電流値が著しく低く反応生成物量が評価系の検出下限界（３％）を下回ったため記録なしとしている。これは、１８０℃という高い温度条件で熱圧着処理を実施したことで、電解質膜のプロトン交換基が分解されたためと考えられる。 Furthermore, Table 1 shows the measured proton conduction resistance of the electrolyte membrane 6 . In Examples 1-5 and 7-11, the resistance was as low as 3.0 to 3.5 Ω, and it was confirmed that the effect of reducing the proton conduction resistance was not lost even after the thermocompression bonding. On the other hand, in Examples 6 and 12, the ion conduction resistance of the electrolyte membrane 6 increased to 360Ω. As a result, the current value between the electrodes was remarkably low, and the amount of the reaction product fell below the lower detection limit (3%) of the evaluation system. It is considered that this is because the proton exchange group of the electrolyte membrane was decomposed by performing the thermocompression bonding treatment at a high temperature condition of 180°C.
　以上説明したように、本実施形態によれば、本実施形態の多孔質電極支持型電解質膜２０は、電解質膜６と、電解質膜６上に直接接合された多孔質還元電極５を有し、多孔質還元電極５の平均気孔径が１μｍ以上とする。これにより、電極内での二酸化炭素の拡散抵抗を低減し二酸化炭素の気相還元の効率を向上できる。また、電解質膜６と多孔質還元電極５とを接合する工程で、加熱しながら圧力を加えて、電解質膜６の膨潤を抑制することで、多孔質電極支持型電解質膜２０の寿命を向上できる。 As described above, according to this embodiment, the porous electrode-supported electrolyte membrane 20 of this embodiment has the electrolyte membrane 6 and the porous reduction electrode 5 directly bonded onto the electrolyte membrane 6, The average pore size of the porous reduction electrode 5 is set to 1 μm or more. As a result, the diffusion resistance of carbon dioxide in the electrode can be reduced, and the efficiency of vapor phase reduction of carbon dioxide can be improved. In addition, in the step of bonding the electrolyte membrane 6 and the porous reduction electrode 5, pressure is applied while heating to suppress swelling of the electrolyte membrane 6, thereby improving the service life of the porous electrode-supported electrolyte membrane 20. .
　多孔質電極支持型電解質膜　２０
　多孔質還元電極　５
　電解質膜　６ Porous electrode-supported electrolyte membrane 20
Porous reduction electrode 5
electrolyte membrane 6

Claims (4)

  1. 　二酸化炭素を還元する気相還元装置に用いられる多孔質電極支持型電解質膜であって、
    　電解質膜と、
    　前記電解質膜上に直接接合された多孔質還元電極を有し、
    　前記多孔質還元電極の平均気孔径が１μｍ以上である
    　多孔質電極支持型電解質膜。     A porous electrode-supported electrolyte membrane used in a gas-phase reduction device for reducing carbon dioxide,
    an electrolyte membrane;
    having a porous reduction electrode directly bonded onto the electrolyte membrane;
    A porous electrode-supported electrolyte membrane, wherein the porous reduction electrode has an average pore diameter of 1 μm or more.
  2. 　請求項１に記載の多孔質電極支持型電解質膜であって、
    　前記電解質膜は、前記多孔質還元電極を重ねて熱圧着され、膨潤が抑制された多孔質電極支持型電解質膜。     The porous electrode-supported electrolyte membrane according to claim 1,
    The electrolyte membrane is a porous electrode-supported electrolyte membrane in which the porous reduction electrode is stacked and thermocompression bonded to suppress swelling.
  3. 　二酸化炭素を還元する気相還元装置に用いられる多孔質電極支持型電解質膜の製造方法であって、
    　電解質膜を沸騰硝酸および沸騰純水へ浸漬する工程と、
    　前記電解質膜の表面上に多孔質還元電極を重ねて熱圧着する工程を有し、
    　熱圧着後の前記多孔質還元電極の平均気孔径が１μｍ以上である
    　多孔質電極支持型電解質膜の製造方法。     A method for producing a porous electrode-supported electrolyte membrane for use in a gas-phase reduction device for reducing carbon dioxide, comprising:
    immersing the electrolyte membrane in boiling nitric acid and boiling pure water;
    a step of thermally compressing a porous reduction electrode overlaid on the surface of the electrolyte membrane;
    A method for producing a porous electrode-supported electrolyte membrane, wherein the porous reduction electrode after thermocompression bonding has an average pore diameter of 1 μm or more.
  4. 　請求項３に記載の多孔質電極支持型電解質膜の製造方法であって、
    　前記熱圧着の加熱温度を１００℃以上１８０℃未満とする多孔質電極支持型電解質膜の製造方法。     A method for producing a porous electrode-supported electrolyte membrane according to claim 3,
    A method for producing a porous electrode-supported electrolyte membrane, wherein the heating temperature for thermocompression bonding is 100°C or higher and lower than 180°C.
PCT/JP2021/019363 2021-05-21 2021-05-21 Porous-electrode-supporting electrolyte membrane and method for producing porous-electrode-supporting electrolyte membrane WO2022244234A1 (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title
PCT/JP2021/019363 WO2022244234A1 (en) 2021-05-21 2021-05-21 Porous-electrode-supporting electrolyte membrane and method for producing porous-electrode-supporting electrolyte membrane
JP2023522159A JPWO2022244234A1 (en) 2021-05-21 2021-05-21

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/JP2021/019363 WO2022244234A1 (en) 2021-05-21 2021-05-21 Porous-electrode-supporting electrolyte membrane and method for producing porous-electrode-supporting electrolyte membrane

Publications (1)

Publication Number Publication Date
WO2022244234A1 true WO2022244234A1 (en) 2022-11-24

Family

ID=84140344

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/JP2021/019363 WO2022244234A1 (en) 2021-05-21 2021-05-21 Porous-electrode-supporting electrolyte membrane and method for producing porous-electrode-supporting electrolyte membrane

Country Status (2)

Country Link
JP (1) JPWO2022244234A1 (en)
WO (1) WO2022244234A1 (en)

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2012128148A1 (en) * 2011-03-18 2012-09-27 国立大学法人長岡技術科学大学 System for reducing and fixing carbon dioxide, method for reducing and fixing carbon dioxide, and method for producing useful carbon resource
WO2019065258A1 (en) * 2017-09-27 2019-04-04 積水化学工業株式会社 Carbon dioxide reduction device, and porous electrode
JP2020023726A (en) * 2018-08-06 2020-02-13 富士通株式会社 Carbon dioxide reducing electrode and carbon dioxide reducing device
WO2020121556A1 (en) * 2018-12-10 2020-06-18 日本電信電話株式会社 Carbon dioxide gas-phase reduction device and carbon dioxide gas-phase reduction method
JP2021059760A (en) * 2019-10-08 2021-04-15 株式会社豊田中央研究所 Co2 reductive reaction apparatus

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2012128148A1 (en) * 2011-03-18 2012-09-27 国立大学法人長岡技術科学大学 System for reducing and fixing carbon dioxide, method for reducing and fixing carbon dioxide, and method for producing useful carbon resource
WO2019065258A1 (en) * 2017-09-27 2019-04-04 積水化学工業株式会社 Carbon dioxide reduction device, and porous electrode
JP2020023726A (en) * 2018-08-06 2020-02-13 富士通株式会社 Carbon dioxide reducing electrode and carbon dioxide reducing device
WO2020121556A1 (en) * 2018-12-10 2020-06-18 日本電信電話株式会社 Carbon dioxide gas-phase reduction device and carbon dioxide gas-phase reduction method
JP2021059760A (en) * 2019-10-08 2021-04-15 株式会社豊田中央研究所 Co2 reductive reaction apparatus

Also Published As

Publication number Publication date
JPWO2022244234A1 (en) 2022-11-24

Similar Documents

Publication Publication Date Title
JP7121318B2 (en) Apparatus for gas phase reduction of carbon dioxide and method for gas phase reduction of carbon dioxide
JP5236125B1 (en) How to reduce carbon dioxide
CN112593251B (en) Electrochemical reaction device
WO2012046362A1 (en) Method for reducing carbon dioxide
JP5753641B2 (en) Carbon dioxide reduction apparatus and method for reducing carbon dioxide
JP5236124B1 (en) How to reduce carbon dioxide
JP5641489B2 (en) How to produce alcohol
JP5779240B2 (en) Solar fuel cell
JP7316085B2 (en) Carbon dioxide reductant recovery system and method for producing useful carbon resources using the system
WO2015001729A1 (en) Method for reducing carbon dioxide
JP7273346B2 (en) Gas phase reduction method of carbon dioxide
WO2022244234A1 (en) Porous-electrode-supporting electrolyte membrane and method for producing porous-electrode-supporting electrolyte membrane
WO2023095203A1 (en) Method for producing porous electrode–supporting electrolyte membrane
WO2023095201A1 (en) Porous electrode-supporting electrolyte membrane and production method for porous electrode-supporting electrolyte membrane
WO2023095193A1 (en) Porous electrode–supporting electrolyte membrane and method for producing porous electrode–supporting electrolyte membrane
WO2022249276A1 (en) Gas-phase reduction device for carbon dioxide and gas-phase reduction method for carbon dioxide
WO2021234908A1 (en) Vapor-phase reduction device for carbon dioxide and method for producing porous electrode-supported electrolyte membrane
JP7356067B2 (en) Carbon dioxide gas phase reduction device and carbon dioxide gas phase reduction method
WO2022113277A1 (en) Gas-phase reduction apparatus for carbon dioxide, and method for producing porous reduction electrode-supported electrolyte membrane
WO2023084683A1 (en) Electrolyte membrane
WO2022249314A1 (en) Carbon dioxide reduction device
WO2022118364A1 (en) Manufacturing method of electrolyte film supported reducing electrode
WO2023238394A1 (en) Nitride semiconductor photoelectrode
WO2023238387A1 (en) Nitride semiconductor photoelectrode and production method therefor
JP2019151877A (en) Reduction method of carbon dioxide and carbon dioxide reduction apparatus

Legal Events

Date Code Title Description
121 Ep: the epo has been informed by wipo that ep was designated in this application

Ref document number: 21940848

Country of ref document: EP

Kind code of ref document: A1

WWE Wipo information: entry into national phase

Ref document number: 18554303

Country of ref document: US

WWE Wipo information: entry into national phase

Ref document number: 2023522159

Country of ref document: JP

NENP Non-entry into the national phase

Ref country code: DE